The invention relates to a smart card and also to a method of producing such a smart card having a card body and at least one recess arranged therein for receiving at least one chip module having module connections in the edge region of the chip module and a conductive structure body embedded in the card body and having body contact connections, in particular an antenna having antenna connections which are arranged below the edge region of the chip module, according to the preambles of patent Claims 1 and 7.
Such smart cards are generally designed as credit cards, bank cards, electronic wallets, etc. and are used to make transactions without using cash, such as for example to pay transport costs on public transport or to pay a purchase price for goods or services. Furthermore, such a smart card can also be used as an ID card for a contactless access control system.
Smart cards usually have a recess for receiving a chip module which comprises an integrated circuit for storing, processing and/or recognizing information that is exchanged with a device, with the smart card either being inserted into the device or brought into the vicinity thereof.
In addition, contactless smart cards for power and data transmission at relatively low frequencies comprise antennas which are generally laminated into the card body and the antenna connections of which must be electrically connected to module connections of the chip module that is inserted.
Conventionally, there are two methods that are frequently used to produce conductive contacts between module connections and antenna connections lying therebelow in the case of methods for producing dual interface cards. In the so-called ACF method, a hot-melt or thermoplastic adhesive with conductive particles arranged therein is arranged so as to produce an electrical connection between contact connections arranged on the underside of the module and laterally protruding antenna connections arranged therebelow, in which the adhesive is applied to a surface of the card body in the region of the recess into which the chip module is inserted. Following installation of the chip module, the conductive particles produce an electrical contact between the module connections and the antenna connections lying therebelow. For this, the hot-melt or thermoplastic adhesive is heated and cured after it has been applied and following installation of the chip module, taking account of specific values for the parameters of temperature, pressure and duration. Such a method is illustrated for example in DE 197 09 985 A1.
In the event of frequent bending stresses, such cured hot-melt and thermoplastic adhesives, which at the same time produce a mechanical connection between chip module and card body, result in a loosening of the electrical connections on account of the plastic and elastic deformability properties of the hot-melt and thermoplastic adhesives. The result is an electronically unreliable connection in the smart card, which for example is of the dual interface type.
DE 197 47 388 C1 discloses another method for the electrical connection of antenna connections and chip module connections using a conductive liquid adhesive. In a recess (cavity) within the card body that is provided for receiving the chip module, at least one bore is made from an edge adhesive region, provided for the adhesion of the chip module, to the antenna connections lying therebelow, in order to introduce into said bore, in a metered manner, a conductive liquid adhesive. Following such a metering, the chip module is placed directly thereon using an adhesive applied to the adhesive region. The adhesive is cured at a predetermined temperature by the action of heat or, if two-component adhesives are used, by exothermic reactions. On account of its stiff and hard properties and also different adhesion properties with respect to the parts that are to be connected, such adhesives frequently exhibit, in the event of frequently occurring dynamic loads as may arise as a result of the smart card being wrongly pushed into a cash machine or as a result of the smart cards being kept in a wallet that is designed to be flexible per se, breaks in the cohesion and/or adhesion in the adhesive on account of overstretching and fatigue phenomena.
Accordingly, it is an object of the present invention to provide a smart card having an inserted chip module and a conductive structure body, such as an antenna, integrated in the smart card, which ensures a permanent electrical connection between chip module connections and body contact connections even in the event of high and frequent bending stress, and also to provide a method of producing such a smart card.
This object is achieved by a smart card having the features of patent Claim 1 and by a production method having the features of patent Claim 7.
An essential point of the invention is that, in a smart card having a card body, at least one recess arranged therein for receiving at least one chip module having module connections in the edge region of the chip module and a conductive structure body embedded in the card body, such as an antenna having antenna connections which are arranged below the edge region of the chip module, with the chip module installed between the module connections on the one hand and the body contact connections on the other hand, adhesive parts made of elastic, conductive material are arranged between the connections with pressure being applied to produce a contact. Such adhesive parts are preferably applied at points to the body contact connections or the module connections and cured prior to installation of the chip module. The chip module is then installed in the card body, as a result of which the adhesive parts are pressed together as a resilient buffer between the connections and produce a permanent, flexible, electrical contact between the module connections and the body contact connections on account of their elastic properties.